Locking mechanism



Feb. 4,1941. y w. J. LANDEN LOCKING MEGHANI SM `Filed Jam.v 16, 1940 Att xjrnay Patented Feb. 4, 1941 UNITED n STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 3'70 0. G. 757) The invention described herein may be manufactured and used by or for the Goverment for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a locking mechanism, applicable, for example, in providing head space adjustment for firearms.

Head space is the measure of the length of the large part of the cartridge chamber, considering the face of the bolt, when locked, as the rear end. Variations from this length is likely to result in malfunctionsif shorter, through failure to breech properly; and if larger, through ruptured cartridge cases. In case of excess head space, even though there be no actual rupture of cases, a terric pound results, and this is very severe in its eiiect on the mechanism. If sunicient to cause a rupture, the gun is then completely out of action, as the forward end of the case remains in the chamber after the extracting movement of the bolt and thereby prevents entry of the next cartridge. If the head space is too great but still not enough so as to cause ruptures, the cases will frequently show incipient ruptures and stretches The purpose of this invention is to provide a simple and easily operable mechanism for establishing correct head space. The invention is characterized by an adjusting screw which serves to x the longitudinal position of a breech bolt and which is securely held Iin place by a novel locking arrangement.

The specilic nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as sho-Wn in the accompanying drawing in which:

Fig. 1 is a plan view of a breech bolt shown in` the closed and locked position;

Fig. 2 is a sectional View on the line 2-2 of Fig. l, and,

Fig. 3 is a sectional view on the line 3 3 of Fig. 2.

Referring to the drawing by characters of reference there is shown a rifle bolt comprising a rear handle portion 5 and a front breech closing portion 6. The handle portion 5 includes a lug I whose iront part has a groove 8 for receiving a coupling flange on the front portion 6 and whose rear face 9 projects laterally to be disposed in front of a locking shoulder Ill on the receiver II when the Ibolt is rotated while in its forward or in-battery position.

In the conventional bolt-action rifle the locking shoulder or the rear face 9 of the locking lug is arranged to provide a camming action to facilitate movement of the bolt into locking position. When the bolt is locked the engagement of the lug and the locking shoulder determine the lbreech closing position of the front face of the bolt.

In order to provide for head space adjustment the locking lug 'I is formed with a longitudinally disposed passage I2 having a reduced threaded bore I3 in its iront part and an enlarged smooth bore Ii in its rear part. An adjusting screw l5 having a threaded portion I6 for engagement with the threaded bore I3 is formed with an enlarged head I'I which is disposed in the smooth bore I4. The front end of the screw is provided with a recess i3 for receiving a tool whereby the screw is rotated to longitudinally position the rear' face I9 of the head Il'. In this invention the face i9 engages the locking shoulder It and determines the head space adjustment.

The head Il is formed with an annular row of teeth 20 having the saine pitch as the threads oi a transversely disposed locking screw 2| which is threaded in the lug. The teeth 20 have a length in excess of the diameter of the locking screw 2l to provide for' engagement of screw 2". and teeth 2u over a relatively large range of ,M

displacement of the adjusting screw I5.

The operation of varying the head space adjustment or allowing for wear of the parts consists in moving the locking screw 2| out of engagement with the adjusting screw I5, rotating the adjusting screw to alter the relative longitudinal position of the face I9 and then reengaging the locking screw.

While the head space adjusting mechanism has been shown mounted in the bolt it is to be understood that it may alternatively be carried by the receiver.

Iclaim:

1. A breech bolt for a firearm, a projecting locking lug on the bolt, an adjusting screw threaded in the lug and having an end projecting from the lug to provide a surface for establishing head space adjustment for the bolt, and means for locking the adjusting screw in place.

2. A breech bolt `for a firearm, a projecting locking lug on the bolt, and an adjusting screw threaded in the lug and having an end projecting from the lug to provide a surface for establishing head space adjustment for the bolt.

3. In a locking mechanism, a support, an adjusting screw threaded in the support and having a projecting portion providing a positioning surface, an annular row of teeth on the adjusting screw, and a locking screw threaded in the support transversely of the adjusting screw and having threads engaging the annular row of teeth on the adjusting screw.

WILLIAM J. LANDEN. 

